Fruit fly white larvae in raspberries

Asked July 16, 2018, 4:54 PM EDT

I haven’t seen the adult but I’m quite sure I have these numerous pests. What chemical can be used & when? Thanks

Washington County Minnesota

3 Responses

Most likely what you have is spotted wing drosophilia (SWD), a relative of the fruit fly that has become an agricultural pest for soft fruits like raspberries.

Unfortunately once the fruit is infested, there isn't really a chemical control to be used - what you will need to do is manage it with cultural controls which include proper garden sanitation and possibly exclusion (netting is a good option.)

Sanitation is important to reduce the local buildup of SWD populations.

  • Frequently harvest crops to ensure ripe fruits are not in gardens for extended periods of time.
  • Remove and destroy any old fruit that remains on stems or that has fallen to the ground.
  • Once infested or fallen fruit has been collected, place it in a plastic bag and seal it tightly.
  • Fruit in clear bags can be left outdoors where the heat from the sun will kill any flies in the bag.
  • Plastic bags can also be placed in the trash.
  • Do not compost this material as that method is unreliable in killing SWD.
  • Do not bury infested material as research has found that SWD can survive being buried as deep as 18 inches.

Please address if the larvae will leave the raspberries after about 15 minutes in warm water. Many exit, but do they all?

I can't really answer that with certainty. The larvae are not harmful to humans if eaten though, so it's not a health concern if some remain in the fruit.